#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <ctype.h>
#include <string.h>

int strverscmp(const char *l0, const char *r0)
{
    const unsigned char *l = (const void *)l0;
    const unsigned char *r = (const void *)r0;
    size_t i, dp, j;
    int z = 1;

    /* Find maximal matching prefix and track its maximal digit
     * suffix and whether those digits are all zeros. */
    for (dp=i=0; l[i]==r[i]; i++) {
        int c = l[i];
        if (!c) return 0;
        if (!isdigit(c)) dp=i+1, z=1;
        else if (c!='0') z=0;
    }

    if (l[dp]!='0' && r[dp]!='0') {
        /* If we're not looking at a digit sequence that began
         * with a zero, longest digit string is greater. */
        for (j=i; isdigit(l[j]); j++)
            if (!isdigit(r[j])) return 1;
        if (isdigit(r[j])) return -1;
    } else if (z && dp<i && (isdigit(l[i]) || isdigit(r[i]))) {
        /* Otherwise, if common prefix of digit sequence is
         * all zeros, digits order less than non-digits. */
        return (unsigned char)(l[i]-'0') - (unsigned char)(r[i]-'0');
    }

    return l[i] - r[i];
}
